Exposure apparatus and its control method, stage apparatus, and device manufacturing method

ABSTRACT

An exposure apparatus, which includes a projection optical system for forming an image of a pattern formed on a master plate, a substrate stage for holding and moving a substrate to be exposed to an imaging position, a position measurement device for measuring a position of the master plate or substrate or relative positions of the master plate and substrate, an alignment device for moving the master plate or substrate on the basis of a measurement value of the position measurement device to adjust the position or relative positions, a main body structure for holding the projection optical system, the substrate stage, and the position measurement device, and a support base for supporting the main body structure. The apparatus includes a measurement device for measuring a variation amount of a principal force acting between the main body structure and the support base or a physical quantity acting on the main body structure, and a correction device for correcting a measurement value of the measurement device using a correction vector obtained by multiplying the measurement result of the measurement device by a predetermined coefficient matrix.

This is a continuation-in-part application of U.S. patent applicationSer. No. 09/094,503 filed on Jun. 10, 1998 abandoned entitled “EXPOSUREAPPARATUS AND ITS CONTROL METHOD, AND DEVICE MANUFACTURING METHOD”.

BACKGROUND OF THE INVENTION

The present invention relates to an exposure apparatus such as anexposure apparatus (so-called a stepper) for sequentially projecting andforming an electronic circuit pattern on a reticle surface onto a wafersurface by step & repeat exposure via a projection optical system in themanufacture of semiconductor elements such as ICs, LSIs, and the like,an exposure apparatus (so-called a scanner) for similarly sequentiallyprojecting and forming an electronic circuit pattern on a reticlesurface onto a wafer surface by step & scan exposure via a projectionoptical system, and the like, and so on, and a device manufacturingmethod that uses the exposure apparatus and, more particularly, to anexposure apparatus used in the manufacture of semiconductor elements,which is hardly influenced by deformation of the main body structure bydetecting in advance the relationship between the deformation state ofthe main body structure and stage precision, and in actual exposureadequately measuring the deformation state and correcting the alignmentmeasurement value and alignment position of a shot in real time, and adevice manufacturing method using the apparatus.

The present invention further relates to a high-speed, high-precisionalignment stage apparatus which can be suitably applied to, e.g.,reticle and wafer moving stages of semiconductor exposure apparatuses,an exposure apparatus having the alignment stage apparatus, and a devicemanufacturing method of manufacturing a device using this exposureapparatus.

In recent years, as semiconductor integrated circuits such as ICs, LSIs,and the like continue to shrink in feature size, a projection exposureapparatus is required to have further improved image performance,superposing precision, throughput, and the like. The superposingprecision can be roughly classified into global components of the shotmatrix within a wafer and components within each shot. The formercomponents can be generally subdivided into a wafer shift component,wafer magnification component, wafer rotation component, orthogonalitycomponent, and the like. The latter components can be generallyaccounted for by a shot (chip) magnification component, shot (chip)distortion component, shot (chip) rotation component, and the like.Among these errors, error components produced by deformation of the mainbody structure have gradually surfaced due to improvements of theapparatus performance.

The error components produced by deformation of the structure areclassified into static components reproduced every time wafer andreticle stages move, and dynamic components such as heat, repulsiveforce due to step & scan exposure, and the like, which are hard toreproduce.

In order to remove these error components, conventionally, the rigidityof the main body structure is increased; a structure which does notdeform even when an external force is slightly applied to the structure,or a structure which does not follow disturbance vibrations due toraised natural frequency is exploited. However, as the rigidity of themain body increases, the weight increases accordingly, and a design thatcan attain both a weight reduction and high rigidity becomes hard toachieve. When a product is designed in consideration of only highrigidity of the main body, evidently the weight of the main body becomeslarge, and the obtained product is hard to handle in terms of carryingout/in, installation, and the like of the apparatus.

As measures against heat that have been conventionally taken, the heatsource of the apparatus is cooled, its heat generation amount isreduced, a low thermal expansion material is used in a structure, and soon. However, there are more than one heat source in the apparatus, andit is impossible to cool all these sources. Furthermore, even whenmeasures against heat conduction or transfer from the heat sources aretaken, an effective measure cannot often be taken for radiation, andthermal influences remain unsolved. Also, the use of a low thermalexpansion material in the structure results in higher cost than a normalmaterial, and yet the thermal influences of the heat sources cannot beperfectly removed.

As described above, deformation factors of the main body include dynamicfactors such as vibrations, forces, and the like, and thermal factors.

In the former factors, dynamic and static deformations attributed to therepulsion forces of the stages that support the main body structure, anddynamic and static deformations caused by a vibration control/vibrationreduction device used for the purpose of controlling vibrations of themain body upon driving of the stages have large components. Of thesecomponents, alignment measurement data, print data, and the likeindicate that the deformation component due to the force applied to themain body by the vibration control/vibration reduction device to controlvibrations of the main body is by no means negligible. Since thisdeformation component is inevitable in terms of the function of thevibration control/vibration reduction device as long as the stages aredriven, it is impossible to set the deformations of the main bodystructure to zero.

The latter factors include changes in ambient temperature, changes intemperature of various heat sources, and the like. Especially, anon-steady process from when the thermal equilibrium state is brokenuntil the thermal equilibrium state is reached again is important forthe thermal factors. Since it is impossible to perfectly recognize thethermal behaviors of the individual heat sources and a cooling sourcesuch as air in the apparatus, such a non-steady process is produced moreor less as long as the apparatus is in operation and processing wafers.Hence, it is impossible to set deformations of the main body structurearising from thermal expansion or shrinkage to zero.

On the other hand, alignment stage apparatuses used in semiconductorexposure apparatuses are required to have high alignment precision inorder to mount position control targets such as wafers and reticles, andthus widely adopt a stage position measurement means using a combinationof a high-resolution laser interferometer and laser mirror.

However, since the position control point and position measurement pointdo not coincide with each other, deformations arising from changes intemperature and changes in stress cause position measurement errors.

To solve this problem, Japanese Patent Laid-Open No. 4-291910 disclosesa method of correcting variations in distance between the positioncontrol point and position measurement point. More specifically, asshown in FIG. 26, variations in distance between a laser mirror 2101 asa position measurement target and a wafer 2102 as a position controltarget are measured by an electric micrometer 2106, and the measurementvalues are added to an alignment laser target value.

Even this method cannot correct measurement errors produced bydeformation and inclination of a fixing jig 2105 for fixing the electricmicrometer 2106 to a top table 2104. That is, since measurement errorscannot be completely corrected as far as an additional criticaldimension measurement sensor is used, variations in distance between theposition control point and position measurement point must be accuratelycorrected without using any additional critical dimension measurementsensor.

Of these errors, measurement errors due to changes in temperature can beprevented by using a low thermal expansion material, a temperatureadjustment device, and the like. However, high stage speeds for a shortmoving time increase measurement errors due to elastic deformation, sothat demands have arisen for correction of variations in distance due toelastic deformation of the stage.

It is still another object of the present invention to correct alignmentmeasurement errors, focus measurement errors, stage position measurementerrors, and the like arising from elastic deformation of a projectionmain body structure in real time in consideration of the fact that theelastic deformation and measurement errors due to the elasticdeformation represent the linear sum of operating forces which cause theelastic deformation.

It is still another object of the present invention to accuratelycorrect variations in distance between the position control point andposition measurement point due to elastic deformation of the stage.

SUMMARY OF THE INVENTION

It is an object of the present invention to attain accurate alignmentirrespective of deformations of the main body structure in considerationof the conventional problems. It is another object of the presentinvention to improve exposure precision of an exposure apparatus withoutimpairing the function of the vibration control/vibration reductiondevice.

In order to achieve the above object, according to the presentinvention, even when the structure has deformed, the deformation ismeasured, and alignment data is adequately corrected based on themeasurement result, in place of the effort of making strains ordistortions (deformations) of the main body structure due to dynamicfactors such as vibrations, forces, and the like, and thermal factorsclose to zero.

More specifically, according to the present invention, an exposureapparatus, which comprises a substrate stage for holding and moving asubstrate, position measurement means for measuring a position of thesubstrate stage, and control means for performing drive control of thesubstrate stage to align the substrate on the basis of the measuredposition, aligns the substrate and a master plate, and forms a patternon the master plate on the substrate by exposure, comprises strainmeasurement means for measuring strain of a structure to which theposition measurement means is fixed, and the control means aligns thesubstrate by the drive control of the substrate stage in considerationof the measured strain.

Also, according to the present invention, a control method for anexposure apparatus, which comprises a substrate stage for holding andmoving a substrate, position measurement means for measuring a positionof the substrate stage, and control means for performing drive controlof the substrate stage to align the substrate on the basis of themeasured position, aligns the substrate and a master plate, and forms apattern on the master plate on the substrate by exposure, comprises thestrain measurement step of measuring strain of a structure to which theposition measurement means is fixed, and the control means aligns thesubstrate by the drive control of the substrate stage in considerationof the measured strain.

Furthermore, according to the present invention, a device manufacturingmethod for aligning a substrate held on a substrate stage by measuring aposition of the substrate stage using position measurement means andcontrolling the position of the substrate stage based on the measuredposition, and for forming a pattern on a master disk onto the substrateby exposure, comprises the steps of: measuring strain of a structure towhich the position measurement means is fixed; and aligning thesubstrate by the position control of the substrate stage inconsideration of the measured strain.

In order to achieve the other object, according to the presentinvention, in an exposure apparatus which comprises a projection opticalsystem, a substrate stage which is movable in a direction perpendicularto the optical axis of the projection optical system while carrying asubstrate, a main body structure for supporting the projection opticalsystem and substrate stage, and a vibration reduction device forsupporting the main body structure and reducing vibration from a floor,when the substrate stage is aligned to sequentially move the substrateset on the substrate stage in turn to a plurality of predetermined shotpositions, a force that the vibration reduction device imposes on themain body structure is measured, and an alignment error and/or stagealignment data are/is corrected on the basis of the measurement result.After the substrate stage is aligned to each shot position of thesubstrate, the circuit pattern on a master plate is illuminated withillumination light of a predetermined wavelength, thereby projecting andforming by exposure the circuit pattern on the substrate on thesubstrate stage via the projection optical system.

According to the present invention, a control method for an exposureapparatus, which comprises a projection optical system, a substratestage which is movable in a direction perpendicular to an optical axisof the projection optical system while carrying a substrate, a main bodystructure for supporting the projection optical system and the substratestage, a vibration reduction device for supporting the main bodystructure and reducing vibration from a floor, and control means foraligning the substrate stage to move the substrate mounted on thesubstrate stage in turn to a plurality of predetermined shot positions,illuminating a circuit pattern on a master plate with illumination lightof a predetermined wavelength after the substrate is aligned to eachshot position, and projecting and forming the pattern by exposure ontothe substrate on the substrate stage via the projection optical system,comprises the measurement step of measuring a force that the vibrationreduction device exerts on the main body structure, and the correctionstep of correcting the aligned position of the substrate stage on thebasis of a measurement result at the measurement step.

Also, according to the present invention, a device manufacturing methodwhich uses a projection optical system, a substrate stage which ismovable in a direction perpendicular to an optical axis of theprojection optical system while carrying a substrate, a main bodystructure for supporting the projection optical system and the substratestage, and a vibration reduction device for supporting the main bodystructure and reducing vibration from a floor, and which aligns thesubstrate stage to move the substrate mounted on the substrate stage inturn to a plurality of predetermined shot positions, illuminates acircuit pattern on a master plate with illumination light of apredetermined wavelength after the substrate is aligned to each shotposition, and projects and forms the pattern by exposure onto thesubstrate on the substrate stage via the projection optical system,comprises the measurement step of measuring a force that the vibrationreduction device exerts on the main body structure, and the correctionstep of correcting the aligned position of the substrate stage on thebasis of a measurement result at the measurement step.

Other features and advantages of the present invention will be apparentfrom the following description taken in conjunction with theaccompanying drawings, in which like reference characters designate thesame or similar parts throughout the figures thereof.

According to the present invention, an exposure apparatus, whichcomprises a projection optical system such as a projection lens forforming an image of a pattern formed on a master plate such as areticle, a substrate stage for holding and moving a substrate to beexposed such as a semiconductor wafer to an imaging position, positionmeasurement means for measuring a position of the master plate orsubstrate or relative positions of the master plate and substrate,alignment means for moving the master plate or substrate on the basis ofa measurement value of the position measurement means to adjust theposition or relative positions, a main body structure for holding theprojection optical system, the substrate stage, and the positionmeasurement means, and a support base for supporting the main bodystructure, comprises means for measuring a variation amount of aprincipal force acting between the main body structure and the supportbase or a physical quantity proportional to the variation amount, andcorrection means for correcting a measurement value of the measurementmeans using a correction vector obtained by multiplying the measurementresult of the measurement means by a predetermined coefficient matrix.

In preferred embodiments of the present invention, the measurement meansis a stage position measurement device for measuring a position of thesubstrate stage, a focus measurement device for measuring a shift inposition or posture of a substrate surface with reference to the imagingposition, an alignment scope for measuring an alignment mark on thesubstrate so as to superpose a new pattern on a pattern which has beenprinted on the substrate surface, or the like. The alignment scope is aTTL on-axis alignment scope for measuring relative positions ofalignment marks on the master plate and substrate using light passing onan optical axis of the projection optical system, a TTL off-axisalignment scope for measuring the relative positions of the alignmentmarks on the master plate and substrate using light passing off theoptical axis of the projection optical system, an off-axis alignmentscope for measuring the position of the alignment mark on the substrateoutside the projection optical system, a reticle alignment scope formeasuring a position of a reticle using a mark on a reticle as a masterplate, or the like. To align the reticle, the alignment scope furthercomprises a reticle stage for holding and moving the reticle.

The predetermined coefficient matrix is estimated by measuring by themeasurement means the position of the substrate on the substrate stagealigned and controlled to keep a position and posture constant, at thesame time applying a forced operating force to respective portions forsupporting the main body structure, and regressively analyzing avariation amount of a measurement value of the measurement means withrespect to variations in the forced operating force.

Also, according to the present invention, a stage apparatus comprises astage for holding and moving an object, stage position measurement meansfor measuring a position of the stage, a sensor for measuring avariation amount of a principal force acting on the stage or a physicalquantity proportional to the variation amount, and means for correctinga measurement value of the stage position using a correction vectorobtained by multiplying a measurement result of the sensor by apredetermined coefficient matrix.

The stage position measurement means may comprise a laser interferometerand a reflecting mirror.

In general, the apparatus further comprises position measurement meansarranged in addition to the stage position measurement means, and thepredetermined coefficient matrix is obtained by regressively analyzing avariation amount of a stage drive force of each axis when the stage ismoved or a physical quantity proportional to the variation amount, and adifference between measurement values of the position measurement meansand the stage position measurement means.

The sensor can be either one of means for monitoring a current value ofa motor for driving the stage and a load cell or strain gauge arrangedat a portion where a drive repulsion force of the motor acts.

Further, according to the present invention, there are provided anexposure apparatus comprising the stage apparatus and means for exposinga wafer or reticle mounted on the stage apparatus, and a devicemanufacturing method comprising the step of manufacturing a device usingthis exposure apparatus.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram showing principal units of a semiconductorexposure apparatus to which the present invention is applied;

FIG. 2 is a front view showing a state wherein a strain gauge, which isimportant in the present invention, is adhered to a main body structureof the apparatus shown in FIG. 1;

FIG. 3 is a sectional view taken along a line A-A′ of FIG. 2 when viewedfrom the -z direction;

FIG. 4 is a front view showing deformation of the main body structuredue to stage stepping;

FIG. 5 is a front view showing thermal deformation of the main bodystructure;

FIG. 6 is a flow chart showing the exposure sequence in the apparatusshown in FIG. 1 to which the present invention is applied;

FIG. 7 is a sectional view showing a state wherein a strain gauge, whichis important in the present invention, is adhered to a main bodystructure in the third embodiment of the present invention;

FIG. 8 is a sectional view showing another state wherein a strain gauge,which is important in the present invention, is adhered to a main bodystructure in the third embodiment of the present invention;

FIG. 9 is a flow chart showing the exposure sequence according to thesecond embodiment of the present invention;

FIG. 10 is a front view for explaining the principles of the presentinvention;

FIG. 11 is a front view for explaining correction of focus measurementerrors in a semiconductor exposure apparatus according to the fifthembodiment of the present invention;

FIG. 12 is a front view showing the stage of the semiconductor exposureapparatus in FIG. 11;

FIG. 13 is a sectional view showing the stage of the semiconductorexposure apparatus in FIG. 11;

FIG. 14 is a diagram showing a support leg with a vibration reductionfunction in the semiconductor exposure apparatus according to the fifthembodiment;

FIG. 15 is a front view for explaining correction of TTL off-axisalignment measurement errors according to the sixth embodiment of thepresent invention;

FIG. 16 is a front view for explaining correction of off-axis alignmentmeasurement errors according to the seventh embodiment of the presentinvention;

FIG. 17 is a front view for explaining correction of reticle alignmentmeasurement errors according to the eighth embodiment of the presentinvention;

FIG. 18 is a front view for explaining correction of TTL on-axisalignment measurement errors according to the ninth embodiment of thepresent invention;

FIG. 19 is a front view showing a semiconductor exposure apparatusaccording to the 10th embodiment;

FIG. 20 is a front view showing the stage of the semiconductor exposureapparatus according to the 10th embodiment;

FIG. 21 is a sectional view showing the stage of the semiconductorexposure apparatus according to the 10th embodiment;

FIG. 22 is a front view showing a semiconductor exposure apparatusaccording to the 11th embodiment;

FIG. 23 is a front view showing a semiconductor exposure apparatusaccording to the 12th embodiment;

FIG. 24 is a flow chart showing the flow in the manufacture ofmicrodevices;

FIG. 25 is a flow chart showing the flow of the wafer process in detail;and

FIG. 26 is a plan view showing the prior art.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

<First Embodiment>

In the first embodiment of the present invention, a substrate is alignedon the basis of the position detected by an alignment measurement meansprovided to a main body structure to detect the position of apredetermined mark on the substrate.

A master plate stage for aligning a master plate, and a projectionoptical system for projecting a pattern on the master plate onto asubstrate for exposure are placed above the main body structure, andstrain is measured at more than one position of the main body structure.

Alignment considering strain can be made in consideration of, e.g., therelationship between strain obtained in advance, and alignment errorsproduced as a result of substrate alignment regardless of the strain,and strain measured in actual exposure.

Exposure is done by aligning the substrate for a plurality of exposurepositions on the substrate. In this case, the substrate stage is steppedupon aligning to each exposure position. Alignment to each exposureposition may be attained by global alignment on the basis of theposition detected by the alignment measurement means disposed on thestructure to detect the position of a predetermined mark on thesubstrate. In such a case, upon position detection for global alignment,the strain is measured, and the position detection result is correctedon the basis of the measured value. Based on the corrected positiondetection result, the coordinate data of each exposure position isobtained. When the stage is moved to each exposure position based on theobtained coordinate data, the strain may be measured, and the coordinatedata of each exposure position may be corrected based on the measuredvalue to attain alignment to that exposure position. Furthermore, insuch a case, to improve the throughput correction for the positiondetection result, the coordinate data of each exposure position may bemade only when the measured value of strain is equal to or larger than apredetermined value.

Strain measurement is done for strain of the structure between aposition measurement means for the substrate stage, and the projectionoptical system.

According to the first embodiment of the present invention, a pluralityof strain gauges are adhered to the main body structure while focusingon strains (deformations) of the main body structure, and thedeformation state of the structure is measured. The deformation state isalways monitored to obtain in advance the relationship between thedeformation state and alignment errors or stage lattice errors byexperiments or numerical simulations, and correction can be made basedon that relationship in actual processes. The actual processes includethe measurement for global alignment, and stage alignment upon step &repeat exposure. Each strain gauge is adhered to the main body structureat locations important for the measurement system, i.e., between aprojection lens and a laser interferometer (a position measurement meansfor the substrate stage), the position of the projection lens, or a baseportion of the laser interferometer. Alternatively, when therelationship between the strain state and alignment or print errors isobtained in advance, the gauge may be attached to an alignment scopeattachment position, reticle stage attachment position, or the like.

With this arrangement, total deformations of the structure produced notonly by dynamic factors such as vibrations, forces, and the like, butalso by thermal factors are measured, and alignment errors and stagelattice errors arising therefrom can be predicted and corrected. Hence,high superposing (alignment) precision can be maintained independentlyof deformations of the structure. Furthermore, since performancerequired for the structure places an importance not on high rigidity buton high reproducibility, the weight can be prevented from beingunnecessarily increased. Also, since no expensive low thermal expansionmaterial need be used, an increase in cost can also be prevented.

FIG. 1 shows a principal part of a projection exposure apparatus(stepper) according to the first embodiment of the present invention.

In FIG. 1, reference numeral 1 denotes an illumination system, whichilluminates a reticle 2 formed with a Cr-deposited circuit pattern. Theillumination system 1 comprises an ultra high-pressure mercury lamp orexcimer laser, shutter, illumination optical system, and the like (noneof them are shown). Reference numeral 3 denotes a substrate that carriesa reticle stage (not shown). The reticle 2 is aligned by a reticle stagedrive mechanism with reference to a mark formed on the reticle stagesubstrate 3. The alignment measurement value is stored in a control unit16 that controls the overall apparatus.

Reference numeral 6 denotes a projection lens for projecting a circuitpattern image on the reticle 2 formed by the illumination system 1 ontoa wafer 18; and 7, a lens drive unit for correcting known changes inimaging performance of the projection lens due to air pressure orexposure. Reference numeral 8 denotes that portion of a main bodystructure which mounts principal units such as the projection lens 6, analignment measurement system, the reticle stage, a wafer stage, and thelike. Note that the main body structure 8 is supported by a vibrationreduction device (not shown). Reference numeral 9 denotes a strain gaugesensor attached to the main body structure 8. The sensor 9 can measurethe deformation state of the main body in real time. Reference numeral 4denotes a mirror for bending the optical path of probe light used inwafer alignment measurement by an off-axis TTL (Through The Lens)system; and 5, a measurement system therefor. The optical path ofalignment light coming from the measurement system 5 is bent through 90°by the mirror 4, and the alignment light enters the projection lens 6 toilluminate an alignment mark formed on the wafer 18. The light reflectedby the alignment mark re-enters the alignment measurement system 5 alongthe same optical path in the reverse direction. In this way, bymeasuring the relative displacement between the alignment mark and areference mark (not shown), alignment measurement is done.

A projector 10 and receiver 11 are elements that constitute a knownfocus wafer tilt detector. The projector 10 irradiates a light beam tomake a small angle with the surface of the wafer 18, and light reflectedby the surface is photoelectrically detected by the receiver 11, therebydetecting the focus position of the projection lens 6 and any tilt ofthe wafer 18. Using this detector, the wafer is aligned in thez-direction using a focus tilt drive function of the wafer stage (to bedescribed later) in units of shots or wafers.

Reference numeral 12 denotes a wafer chuck that vacuum-chucks the wafer18; 13, a θ-z-tilt stage that is coarsely or finely movable in the tilt,θ-, and z-directions; and 15, an x-y stage that is coarsely or finelymovable in the x- and y-directions. The wafer stage is made up of thetilt stage 13 and x-y stage 15. The position of the wafer stage isalways monitored by a laser interferometer bar mirror 17 attached to thetilt stage 13 and a laser interferometer 14.

The entire exposure apparatus is controlled by a control unit 16 as wellas these principal units.

FIG. 4 shows deformation of the main body structure due to mechanicalfactors such as vibrations, forces, and the like, and FIG. 5 showsdeformation due to thermal factors. Since these figures show only mainunits and members associated with the structure deformations of thestepper, the illumination system, reticle stage, alignment measurementsystem, and the like are not shown.

FIG. 4 especially shows deformation of the main body structure due tostepping of the wafer stage. In FIG. 4, reference numeral 6 denotes aprojection lens; 20, a member that joins the projection lens 6 and themain body structure 8; 14, a laser interferometer attached to a column;18, a wafer; 12, a wafer chuck; 17, a bar mirror; 13, a θ-z-tilt stage;15, an x-y stage; and 25, a stage surface plate. Reference numerals 21and 22 denote a vibration control/vibration reduction device (to bereferred to as a mount hereinafter) for controlling vibrations producedby the stage repulsion force and reducing vibrations from the floor.FIG. 4 illustrates only two mounts, but the main body is normallysupported by four or three mounts. Reference numeral 23 denotes a mainbody support plate that supports the main body via the mounts 21 and 22.

The mechanism of static or dynamic deformation of the main bodystructure 8 upon stepping of the wafer stage will be explained belowwith the aid of FIG. 4. When the wafer stage is stepped in thex-direction, the repulsion forces of acceleration and deceleration acton the main body structure 8, and the main body vibrates. In order toquickly control the vibrations, the damping functions of the mounts 21and 22 operate. When these damping functions ideally operate, alignmentmeasurement or exposure after the stepping can be ideally done. However,in practice, the damping functions suffer variations in units ofchannels, or the main body structure 8 is pulled, compressed, or bent inthe horizontal direction depending on the layout and the like of themounts 21 and 22, thus producing unwanted dynamic deformation in themain body structure 8. Static deformation includes that arising from thestage position. When the wafer stage is stepped, the barycentricposition of the projection exposure apparatus main body varies, and themain body tilts. In order to suppress such tilt and maintain the mainbody horizontally, the main body support functions of the mounts 21 and22 operate to apply vertical forces to the main body. As a result,static deformation that depends on the stage position is produced in themain body structure 8. The static deformation is always produced andcannot be prevented unless the main body structure 8 has infinitely highrigidity. As described above, when the wafer stage is stepped, staticand dynamic deformations are produced in the main body structure 8, asshown in FIG. 4.

FIG. 5 similarly shows deformation of the main body structure 8 due tothermal factors. Note that in thermal deformation of the main bodystructure 8, non-steady expansion or shrinkage is produced until theentire apparatus is thermally balanced, and its steady state ismaintained when the apparatus is thermally balanced. Hence, when athermal balance is disturbed by some factors, the deformation statekeeps changing until the steady state is reached again. In addition, theheat capacity of the main body structure 8 is large, and the time andtime constant required until the steady state is reached aresufficiently longer than those of the above-mentioned static and dynamicdeformations produced by the stepping of the stage. Note that thermalfactors include: heat generated by exposure light, heat generated upondriving the stages, heat generated by various measurement devices,outlet air from an ULPA (Ultra Low Penetration Air) filter, and thelike. In FIG. 5, the temperature distribution of the upper portion ofthe main body structure 8 has changed due to these factors, and thestructure 8 has thermally deformed. Thermal deformation is alwaysproduced unless the material of the main body structure 8 has a zerolinear expansion coefficient.

As described above, when the main body structure 8 has deformed due todynamic factors such as vibrations, forces, and the like, and thermalfactors, such deformations largely influence the apparatus performance.That is, since the projection lens and laser interferometer are directlyattached to the main body structure 8, when the main body structure 8has deformed, as shown in FIGS. 4 and 5, the relative distance betweenthe optical axes of the projection lens 6 and interferometer 14 changes.Meanwhile, since the position of the wafer stage is servo-controlled,the wafer stage is always aligned to a target position. Hence, eventhough the measurement result of the laser interferometer is correct,alignment measurement and exposure are done in the presence of positionerrors since the relative distance between the optical axes of theprojection lens 6 and interferometer 14 has changed. When the relativedistance between the optical axes of the projection lens 6 andinterferometer 14 has changed, a lattice pattern is formed by the waferstage according to the measurement values of the interferometer 14,i.e., a stage lattice is formed. That problem becomes serious especiallywhen the stage lattice varies while the apparatus is in operation, thatis, when the stage lattice upon global alignment is different from thatupon step & repeat exposure, or when the stage lattice varies in unitsof layers. In such a case, a shot is printed at a position differentfrom a shot matrix printed in the previous layers, thus lowering thesuperposing precision of the apparatus.

As has already been described above, it is impossible to always reducedeformations of the main body structure 8 arising from dynamic andthermal deformations to zero, and measures that are taken to make suchdeformations closer to zero are not practical since they lead to anincrease in apparatus weight and an increase in cost. In view of suchproblems, in the present invention, deformation of the main bodystructure 8 is measured in real time, and stage lattice and alignmentprecision errors are corrected using the relationship between thedeformations and stage lattice errors or alignment measurement errorsdetermined in advance by experiments, numerical simulations, and thelike based on the measured value.

FIGS. 2 and 3 depict the state wherein sensors for measuring thedeformation state of the main body structure 8, e.g., strain gaugesensors are adhered to the main body structure 8. FIG. 2 is a front viewas in FIGS. 4 and 5, and FIG. 3 is a sectional view taken along a lineA-A′ in FIG. 2, when viewed from the -Z direction. In these figures,reference numerals 14 and 33 respectively denote x- and y-interferometers; and 35, a yaw interferometer used in yaw control of thestage. Reference numerals 9, 32, and 34 denote strain gauges which arerespectively attached between the respective interferometers and theprojection lens 6. The gauges are attached to these positions becausechanges in relative distance between the optical axes of the x- and y-interferometers 14 and 33 and yaw interferometer 35, and the opticalaxis of the projection lens 6 are in question. The strain gauge 9measures the x-component of strain of the main body structure 8 betweenthe x-interferometer 14 and projection lens 6; the strain gauge 32, they-component of strain of the main body structure 8 between they-interferometer 33 and projection lens 6; and the strain gauge 34, they-component of strain of the main body structure 8 between the yawinterferometer 35 and projection lens 6. With such a layout of thestrain gauges, deformation of the main body structure 8, especially,deformations between the respective interferometers and projection lenscan be adequately measured.

A method of obtaining the relationship between the deformations andstage lattice errors, i.e., main body deformation influence coefficientsA (Ax, Ay, Aθ), by experiments, numerical simulations, or the like willbe briefly explained below. Note that Ax, Ay, and Aθ are coefficients,which respectively represent the relationships between the strain of themain body, and errors in the x-, y-, and shot rotation directions in thewafer.

Since the main body deformation influence coefficients A represent therelationship between the strain produced by deformation of the mainbody, and stage lattice errors, a method of acquiring print data whilegiving mechanical deformations to the main body by some method is usedin practice. The outputs from the respective strain gauges in athermally equilibrated state while the wafer stage is locatedimmediately below the projection lens are used as reference outputs (tobe referred to as reference strains hereinafter). Let Δε_(expo.) be thechange amount between the reference strain and strain produced in thestructure when mechanical deformation is given to the main bodystructure 8 by experiments, that is${\Delta ɛ}_{{expo}.} = \begin{bmatrix}{\delta ɛ}_{11} & {\delta ɛ}_{12} & {\delta ɛ}_{13} \\\vdots & \vdots & \vdots \\{\delta ɛ}_{n1} & {\delta ɛ}_{n2} & {\delta ɛ}_{n3}\end{bmatrix}$

Print data obtained simultaneously with the strain is processed toextract only stage lattice error components Data_(expo.) (ΔX_(expo.),ΔY_(expo.), Δθ_(expo.)) that have varied due to the main bodydeformation. ${Data}_{{expo}.} = \begin{bmatrix}{{\Delta \quad X_{{expo}.}}\quad} \\{\Delta \quad Y_{{expo}.}} \\{\Delta\theta}_{{expo}.}\end{bmatrix}$

${{\Delta \quad X_{{expo}.}} = \begin{bmatrix}{\delta \quad X_{1}} \\\vdots \\{\delta \quad X_{m}}\end{bmatrix}},\quad {{\Delta \quad Y_{{expo}.}} = \begin{bmatrix}{\delta \quad Y_{1}} \\\vdots \\{\delta \quad Y_{m}}\end{bmatrix}},\quad {{\Delta\theta}_{{expo}.} = \begin{bmatrix}{\delta\theta}_{1} \\\vdots \\{\delta\theta}_{m}\end{bmatrix}}$

For n=3 m.

Since errors produced by microscopic deformation of the main bodystructure 8 are in question, these two variables Data_(expo.) andΔε_(expo.) can be assumed to have a linear relationship. Using the mainbody deformation influence coefficients A (Ax, Ay, Aθ) as those for suchlinear equation, we have

Data_(expo.)=Δε_(expo.) ·A+Err _(expo)

where Err_(expo) is random errors.

Hence, the main body deformation influence coefficients A that canminimize Err_(expo) can be obtained from this formula using the methodof least squares.

In the above description, the influence coefficients are obtained by themethod of acquiring print data while giving mechanical deformation bysome method. Likewise, these coefficients can be obtained by otherexperimental methods or numerical simulations. For example, a method ofgiving mechanical deformation to the main body while observing the markon the wafer using the measurement system (alignment scope) 5 may beused. Let Data_(a.s.) (ΔX_(a.s.), ΔY_(a.s.), Δθ_(a.s.)) be errorcomponents due to the deformation, which can be calculated from dataobtained by the observation result, and Δε_(a.s.) be the main bodystrain at that time. Then, these two variables satisfy the followingrelation via the main body deformation influence coefficients A (Ax, Ay,Aθ):

Data_(a.s.)=Δε_(a.s.) ·A+Err _(a.s.)

Hence, as in the above-mentioned method, the main body deformationinfluence coefficients A (Ax, Ay, Aθ) that can minimize Err_(a.s.) canbe obtained from this formula using the method of least squares.

As a method using numerical simulations, strain Δε_(sim.) at the adheredposition of the strain gauge, and x- and y-direction magnificationrotation error Data_(sim.) (ΔX_(sim.), ΔY_(sim.), Δθ_(sim.)) which canbe calculated from changes in relative distance between theinterferometer optical axes and projection lens optical axes uponapplying an imaginary force on an FEM model of the main body structure8, are calculated. These two variables satisfy the following relationvia the main body deformation influence coefficients A (Ax, Ay, Aθ):

Data_(sim.)=Δε_(sim.) ·A+Err _(sim.)

In numerical simulations, since the two variables strictly satisfy alinear relationship, the main body deformation influence coefficients A(Ax, Ay, Aθ) can be immediately obtained without using the method ofleast squares as long as the boundary conditions upon calculations arecorrect as compared to practical ones. The methods of calculating themain body deformation influence coefficients A, which are important inthe first embodiment of the present invention, have been described.

The exposure sequence to which the first embodiment of the presentinvention is applied will be described below with reference to FIG. 6.When the sequence is started (step 40), a reticle is loaded onto thereticle stage. The reticle is aligned to the reference mark formed onthe reticle stage substrate (step 41). A wafer is then fed onto thestage (step 42), and is pre-aligned (step 43). Subsequently, a main bodystructure strain measurement as the characteristic feature of thepresent invention is done simultaneously with a global alignmentmeasurement (to be simply referred to as an alignment measurementhereinafter) (step 44).

In the alignment measurement, several specific shots on the wafer areselected as representative measurement points. The number of measurementshots is four for sub measurements and eight for main measurements,although it depends on processes, or main measurements alone are donewhile omitting sub measurements. In the first embodiments, eight shotsfor main measurements alone as the latter case will be examined. In thiscase, the outputs from the respective strain gauges in a thermallyequilibrated state when the wafer stage is located immediately below theprojection lens are used as reference outputs (reference strains), andthe change amounts from the reference strains produced in the main bodystructure during the alignment measurement periods of the respectiveshots are measured. Let Δε (δε_(i1), δε_(i2), δε_(i3), i=1, . . . , 8)be the measured strains. Then, error components Δε· A of the alignmentmeasurement values due to the main body deformation can be immediatelycalculated using the main body deformation influence coefficients Aobtained by the above-mentioned methods. The alignment measurementvalues for eight shots are corrected using these error components Δε· A(step 45). The alignment measurement values corrected in this way aresubjected to statistical processing, which is normally done in globalalignment, thus calculating the coordinate system that considers the x-and y-components of shift, rotation component, and magnificationcomponent of the wafer (step 53). As a matter of course, this coordinatesystem does not include any components produced by the deformation ofthe main body structure.

Then, stepping to each shot is done based on this coordinate system. Thewafer stage is aligned to the target position of the first shot, and atthe same time, strains of the main body structure are measured (step46). That is, strains Δε′ (δε′₁, δε′₂, and δε′₃) of the main bodystructure, which have been produced immediately before exposure, aremeasured, and alignment errors Δε′· A due to the deformation of the mainbody at that shot position are immediately calculated using the mainbody deformation influence coefficients A. Based on these errors, thealignment target value of the shot of interest is corrected (step S47),thus aligning the wafer stage. After that, the shutter is opened, and acircuit pattern is formed by exposure at a predetermined position (step48), thus completing exposure for the first shot. Since exposure for allthe shots is not complete yet (NO in step 49), exposure for the secondshot is started (step 46). The operation for the second shot is made inthe same manner as in the first shot. That is, the wafer stage istemporarily aligned to the target position for the second shotcalculated in step 53, and strains of the main body structure at thattime are measured (step 46). Based on the measurement values, errorcomponents Δε· A due to main body deformation are calculated, and thetarget value is corrected, thus aligning the wafer stage to the positionof the second shot (step 47). Then, exposure for the second shot is done(step 48). In this way, steps 46 to 48 are repeated until exposure forall the shots is complete.

Upon completion of exposure for all the shots (YES in step 49), thewafer is unloaded (step 50). If more wafers to be processed remain,exposure continues (YES in step 51). The sequence returns to step 42 toload a new wafer onto the stage again, and a series of processingoperations (steps 42 to 50) are repeated. Upon completion of theprocessing for all the wafers (NO in step 51), the sequence to which thefirst embodiment of the present invention is applied ends (step 52).

As described above, in the first embodiment, since the strain changeamounts of the main body structure are measured simultaneously withglobal alignment measurement, the correction amounts of the alignmentmeasurement values are calculated from the main body deformationinfluence coefficients A to correct the measurement values, therespective shot coordinate positions are calculated by statisticalprocessing on the basis of the corrected alignment measurement values,and the wafer stage is moved to each shot position based on thecalculated coordinate position. In addition, upon alignment as well,since the strain change amounts of the main body structure are measured,the correction amounts of the respective shot positions are calculatedfrom the main body deformation influence coefficients A, and the shotpositions are corrected. In this way, since errors produced by main bodydeformation are corrected in two steps, i.e., at the times of globalalignment measurement and alignment to each shot position, the matrixprecision of the wafer stage can be improved, and high superposingprecision can be maintained.

<Second Embodiment>

The second embodiment is characterized in that correction is done onlywhen the monitored strains of the main body structure have exceeded apredetermined value in the exposure sequence described in the firstembodiment. The exposure sequence of this embodiment will be explainedbelow with reference to FIG. 9.

When the sequence is started (step 80), a reticle is loaded onto thereticle stage. The reticle is aligned to the reference mark formed onthe reticle stage substrate (step 81). A wafer is then fed onto thestage, and is pre-aligned (step 82). Subsequently, a main body structurestrain measurement as the characteristic feature of the presentinvention is done simultaneously with a global alignment measurement (tobe simply referred to as an alignment measurement hereinafter) (step83). These steps are the same as those in the first embodiment.

In the second embodiment, an allowable maximum strain Δε₀ at each strainmeasurement position of the main body structure, which is allowed foralignment precision and stage lattice errors, is calculated in advance.If the output from each strain gauge has become larger than the strainΔε₀, the alignment measurement precision and stage lattice precisionexceed the specifications of the apparatus.

It is checked in step 84 if the measured strain Δε is larger than theallowable maximum strain Δε₀. If the measured strain is smaller than theallowable maximum strain (NO in step 84), the alignment measurementvalues are subjected to normal statistical processing in step 86 withoutbeing corrected, thus calculating the coordinate positions of therespective shots in the wafer. By contrast, if the measured strain Δε islarger than the allowable maximum strain Δε₀(YES in step 84), thealignment measurement values are corrected using error components Δε· Adue to main body deformation, as in the first embodiment. Using thecorrected alignment measurement values, the coordinate values of therespective shots are statistically calculated (step 86).

Then, stepping to each shot is effected based on this coordinate system.The wafer stage is aligned to the target position of the first shot, andat the same time, strains of the structure are measured (step 87). It ischecked in step 88 if the measured strain Δε′ is larger than theallowable maximum strain Δε₀. If the measured strain is smaller than theallowable maximum strain (NO in step 88), exposure is done withoutchanging the current stage target position (step 90). Conversely, if themeasured strain Δε′ is larger than the allowable maximum strain Δε₀ (YESin step 88), the stage target position is corrected using errorcomponents Δε′· A due to main body deformation, as in the firstembodiment, and exposure is done at the corrected coordinate position(step 90).

Since exposure for all the shots is not complete yet (NO in step 91),exposure for the second shot is started (step 87). The operation for thesecond shot is made in the same manner as in the first shot. In thisway, steps 87 to 90 are repeated until exposure for all the shots iscomplete.

Upon completion of exposure for all the shots (YES in step 91), thewafer is unloaded (step 92). If more wafers to be processed remain,exposure continues (YES in step 93). The sequence returns to step 82 toload a new wafer onto the stage again, and a series of processingoperations (steps 82 to 92) are repeated. Upon completion of theprocessing for all the wafers (NO in step 93), the sequence to which thepresent invention is applied ends (step 94).

In the second embodiment, the allowable maximum strain Δε₀ at eachstrain measurement position of the main body structure, which is allowedfor alignment precision and stage lattice errors, is calculated inadvance, and in actual exposure, when the output from each strain gaugeis larger than Δε₀, correction calculations are made; otherwise,conventional processing is done. With this sequence, the throughput canbe improved at slight cost of superposing precision.

<Third Embodiment>

In the third embodiment, it is important to recognize the relationshipbetween deformation (strain) produced in the main body structure, andstage lattice errors in advance. Hence, as long as the relationshipbetween deformation produced in the main body structure, and stagelattice errors can be recognized, the number and positions of straingauges to be adhered to the main body are not particularly limited. Inthe third embodiment, the number and positions of strain gauges to beadhered are different from the first and second embodiments inconsideration of its feature. FIG. 7 is a sectional view showing thestate of strain gauges adhered to the main body structure, as in FIG. 3.In the first embodiment, the strain gauges 9, 32, and 34 are adheredbetween the respective interferometers and the projection lens tomeasure the x- and y-components of strain, and the y-component of strainbetween the yaw interferometer 35 and the main body structure 8.However, the three strain gauge outputs cannot often satisfactorilyexpress stage lattice error variations, or main body deformationinfluence coefficients A with higher precision need often be obtained.Hence, in the third embodiment, each strain gauge between oneinterferometer and projection lens measures along two axes, i.e., x- andy-directions. In FIG. 7, reference numerals 60, 61, and 62 denote straingauges, each of which can measure in the x- and y-directions.

Similarly, FIG. 8 shows the case wherein strain gauges are evenlyadhered to eight positions to the main body structure surface platearound the projection lens without sticking to the adhesion positionsbetween the respective interferometers and projection lens. Each ofstrain gauges 70 to 77 has a two-axis arrangement (x and y), and canmeasure in the x- and y-strains. Such an arrangement is used to alwaysmonitor strains of the entire surface of the main body structure surfaceplate, and to cope with a case wherein main body strain other than thoseat positions between the respective interferometers and projection lenslargely influences stage lattice errors.

The calculation method of main body deformation influence coefficients Ain such a case is the same as that in the first embodiment, and thecoefficients can be calculated using any of print data, scope data, andnumerical simulation. Using the obtained main body deformation influencecoefficients A, exposure is made according to the exposure sequenceshown in FIG. 6 or 9. As described above, each strain gauge has atwo-axis arrangement to measure strains between the projection lens andinterferometer, or to measure strains of the entire surface of the mainbody structure surface plate, main body deformation influencecoefficients A with higher precision can be calculated, and highsuperposing precision can be realized.

As described above, it is important in the present invention torecognize the relationship between deformation (strain) produced in themain body structure, and stage lattice errors in advance. Hence, as longas the relationship between deformation produced in the main bodystructure, and stage lattice errors can be recognized, the number andpositions of strain gauges to be adhered to the main body are notparticularly limited. Therefore, various patterns other than those inthe third embodiment can be used.

As described above, according to the first to third embodiments of thepresent invention, since the substrate is aligned under drive control ofthe stages in consideration of strains of the main body structure,accurate alignment can be attained irrespective of strains of the mainbody structure.

More specifically, since the strain gauges are adhered to a plurality ofpositions of the main body structure to recognize in advance therelationship between deformations (strains) produced in the main bodystructure, and alignment errors or stage lattice errors, deformations(strains) of the main body structure are monitored in the actualexposure sequence to correct measurement errors due to the deformationsof the main body structure produced upon global alignment, and tocorrect stage alignment errors due to deformations of the main bodystructure produced upon step & repeat exposure, thus realizing highsuperposing precision without being influenced by dynamic and thermaldeformations of the structure. Furthermore, whether or not correction ismade may be determined depending on the magnitudes of strains producedin the main body structure, so as to give priority to throughput overprecision. When the present invention is used, an importance need not beplaced on high rigidity of the structure, and an increase in weight ofthe structure can be suppressed. The present invention can be relativelyeasily practiced by attaching only strain gauge sensors and modifyingmeasurement control system software without requiring large changes indesign.

<Fourth Embodiment>

The fourth embodiment of the present invention focuses on deformationscaused by the functions of a vibration reduction device, and even whenthe main body structure has deformed, the deformations are measured toattain adequate correction based on the measurement result withoutimpairing the functions of the vibration reduction device. In this way,high superposing precision is realized without being influenced by anyvariations in support force of the vibration reduction device.

More specifically, in the fourth embodiment, a sensor that can measurethe force that the vibration reduction device exerts on the structure isattached to measure that force. The applied force is always monitored torecognize in advance the relationship between changes in applied forceand alignment errors or stage lattice errors by experiments, numericalsimulations, or the like, and the measurement values of alignmentmeasurement sensors and stage position measurement sensors are correctedbased on that relationship. The sensor that can measure a force maycomprise a pressure gauge or load cell when the vibration reductiondevice uses a pneumatic spring as an actuator.

Using the above-mentioned means, the force that the vibration reductiondevice exerts on the main body structure is measured, and alignmenterrors or stage lattice errors caused by that force can be predicted.Hence, high superposing precision can be maintained without impairingthe functions of the vibration reduction device independently ofdeformations of the main body structures. As the stage moving speedbecomes higher, the force that the vibration reduction device imposes onthe main body increases. However, in this embodiment, since this forceis always monitored, and error components can be predicted, thethroughput can be improved while maintaining high superposing precision.Furthermore, when the means of this embodiment is used, as theperformance required for the structure places an importance not on highrigidity but on high reproducibility, the weight can be prevented frombeing unnecessarily increased.

In the fourth embodiment, the application force that each mount exertson the main body structure, and the application force upon upwardmovement of the stage are measured in real time, and the relationshipbetween the pressure and stage position errors or alignment measurementerrors is obtained in advance by experiments, numerical simulations, orthe like, thereby correcting stage lattice or alignment precision errorsin real time.

Note that each mount of the fourth embodiment uses compressed air as anenergy source, and realizes a vibration reduction function byfeedback-controlling the internal pressure of a pneumatic springactuator based on, e.g., the acceleration of the main body.

In the fourth embodiment, a shot matrix free from the influences ofvariations in mount pressure can be obtained by an error estimationmethod of the present invention in the process of 1st layer exposure. Inexposure operations for the 2nd layer and subsequent layers, alignmentmeasurement values are corrected by a similar error estimation methodupon global alignment measurement. The corrected alignment measurementvalues are subjected to normal statistical processing to calculatetarget coordinate positions of the respective shots. Movement to eachshot position is made based on the calculated coordinate position. Insuch alignment as well, since the forces applied to the main body aremeasured, the correction amount of each shot position is alwayscalculated by the error estimation method of the present invention, andthe shot position is corrected. In this fashion, since errors producedby variations in force applied to the main body are always corrected inthe processes of shot alignment for the 1st layer, global alignmentmeasurement for the 2nd layer and subsequent layers, and alignment foreach shot position, the matrix precision of the wafer stage can beimproved, and high superposing precision can be maintained.

As a modification of the fourth embodiment, the wafer stage moving speedmay be increased for the purpose of improving the throughput. As theacceleration of the wafer stage becomes larger, the repulsion force thatthe stage applies to the main body also increases, and the force thateach mount applies to the main body increases so as to controlvibrations of the main body. For these reasons, the main body structureis expected to deform. In such a case, in the fourth embodiment, largevariations in mount pressure in the processes of wafer operations, i.e.,in the processes of each shot alignment and alignment measurement, aremeasured, and error components caused by such variations can bepredicted. In this way, the throughput can be greatly improved whilemaintaining high superposing precision of the apparatus.

As described above, according to the fourth embodiment, since therelationship among the mount pressure, alignment errors, and stagealignment errors, that may deform the main body structure, is obtainedin advance, each mount pressure is monitored in the actual exposuresequence to correct measurement errors due to the deformations of themain body structure produced upon global alignment, and to correct stagealignment errors due to the deformations of the main body structureproduced upon step & repeat exposure, thus providing an exposureapparatus which is free from any influences of mount pressure variationsand has high superposing precision.

According to the fourth embodiment of the present invention, since animportance need not be placed on high rigidity of the main bodystructure, an increase in weight of the structure can be prevented. Thepresent invention can be relatively easily practiced by attaching onlystrain gauge sensors and modifying measurement control system softwarewithout requiring large changes in design.

In the following fifth to ninth embodiments, stage position measurementerrors, alignment measurement errors, and focus measurement errors arepredicted and corrected using a vector obtained by measuring principalforces acting on the main body structure or physical quantitiesproportional to them, and any one of the measurement value of a loadcell for measuring the support force of a support base, the measurementvalue of the pressure of a pneumatic spring when a pneumatic spring typevibration reduction mechanism is provided to a contact with the supportbase, and the measurement value of a strain gauge arranged near acontact with the support base, and multiplying these measurement valuesby an appropriate coefficient matrix.

This arrangement can realize a semiconductor exposure apparatus almostfree from the influence of deformation of the main body structure. Thisis because even when the attachment position of a focus measurementdevice for measuring the position and posture of a wafer surface shiftsowing to elastic deformation of the main body structure arising fromchanges in forces for supporting the main body structure or forces forcontrolling vibrations of the main body structure, principal forcesacting on the main body structure which cause the shift are alwaysmeasured to calculate and correct measurement errors caused by the shiftin real time in an exposure apparatus (so-called a stepper) forsequentially projecting and forming an electronic circuit pattern on areticle surface onto a wafer surface by step & repeat exposure via aprojection optical system in the manufacture of semiconductor elementssuch as ICs, LSIs, and the like, or an exposure apparatus (so-called ascanner) for similarly sequentially projecting and forming an electroniccircuit pattern on a reticle surface onto a wafer surface by step & scanexposure via a projection optical system.

The principle of the present invention will be explained briefly. FIG.10 shows a model in which a main body structure expressed by a modelobtained by sandwiching an elastic structure spring 102 having rigidityk1, which represents deformation inside the main body structure, betweena mass point 1 having a mass m1 and a mass point 2 having a mass m2 issupported by a load cell 105 and an elastic support base spring 104having rigidity k2.

Assuming a force f_(a) acting on the mass point l as an external forcecorresponding to the repulsion force of the stage, the motion equationof this model is given by

m ₁ ^({umlaut over (x)}) ₁ +k ₁(x ₁ −x ₂)=f _(a)  (1)

m ₂ ^({umlaut over (x)}) ₂ −k ₁(x ₁ −x ₂)+k ₂ x ₂=0  (2)

Equations (1) and (2) are solved to obtain a vibration equation havingtwo vibration modes. Since k₂x₂ corresponding to a main body structuresupport force is measured by the load cell 105, the measurement value isrepresented by f_(b)=−k₂x₂ to rewrite equation (2) into

m ₂ ^({umlaut over (x)}) ₂ −k ₁(x ₁ −x ₂)=f _(b)  (2′)

If(1)_(—) m ₂−(2)_(—) m ₁ m ₁ m ₂({umlaut over (x)} ₁ −{umlaut over (x)}₂)+(m ₁ +m ₂)k ₁(x ₁ −x ₂)=m ₂ f _(a) +m ₁ f _(b)  (3)

The two sides are divided by m₁m₂ into $\begin{matrix}{{\left( {{\overset{¨}{x}}_{1} - {\overset{¨}{x}}_{2}} \right) + {\frac{\left( {m_{1} + m_{2}} \right)k_{1}}{m_{1}m_{2}}\left( {x_{1} - x_{2}} \right)}} = {\frac{f_{a}}{m_{1}} + \frac{f_{b}}{m_{2}}}} & \left( 3^{\prime} \right)\end{matrix}$

As a result, (x₁−x₂) represents forced vibrations having aminimum-degree natural frequency ω unique to the structure:$\begin{matrix}{\omega = \sqrt{\frac{\left( {m_{1} + m_{2}} \right)k_{1}}{m_{1}m_{2}}}} & (4)\end{matrix}$

If the minimum-degree natural frequency ω is set satisfactorily high byincreasing the rigidity of the main body structure, the influence ofresonance can be removed by short-time averaging in alignmentmeasurement or focus measurement using the mean value of measurementdata.

If the minimum-degree natural frequency ω is set much higher than thestage control frequency band, the influence of resonance on thestructure can be avoided because, even if the influence of resonanceappears in a stage position measurement value, stage control cannotrespond to this.

Since inertia terms can be ignored in a region where the frequency islower than the minimum-degree natural frequency ω, equation (3′) cam berewritten into $\begin{matrix}{\left( {x_{1} - x_{2}} \right) = {\frac{m_{1}m_{2}}{\left( {m_{1} + m_{2}} \right)k_{1}}\left( {\frac{f_{a}}{m_{1}} + \frac{f_{b}}{m_{2}}} \right)}} & (5)\end{matrix}$

Accordingly, in a main body structure not using any flexible supportmechanism such as a mount, the distance between two arbitrary points onthe main body can be represented by the linear sum of all forces actingon the structure within the range up to the minimum-degree naturalfrequency unique to the structure.

More specifically, the distance between the two points of the projectionlens and stage position measurement device, the distance between the twopoints of the projection lens and alignment scope, the distance betweenthe two points of the projection lens and focus measurement device, andthe like can be predicted by the linear sum of all forces acting on thestructure.

However, an accurate linear sum expression, i.e., an accuratecoefficient matrix must be estimated.

To meet this demand, a method of estimating such a coefficient matrixwill be described in detail.

Irregular variations in support forces independent of each other, e.g.,forced variations caused by white noise or sine wave sweep are appliedto all support points for supporting the main body structure. Thevariations in support forces or physical quantities proportional tothem, and the measurement values of the stage position measurementdevice and alignment scope or the stage position measurement device andfocus measurement device are simultaneously recorded.

For example, the measurement value of the focus measurement device isgiven by the measurement value of a z-tilt sensor as part of the stageposition measurement device and the elastic deformation component of themain body structure:

Dx+dx=Dx ₀ +dx ₀ +A(F _(e) +f _(e))+dx _(e) +C  (6)

where

Dx: column vector representing the mean of measurement values of thefocus measurement device

dx: column vector representing variations in measurement values of thefocus measurement device

Dx₀: column vector representing the mean of measurement values of thez-tilt sensor

dx₀: column vector representing variations in measurement values of thez-tilt sensor

A: coefficient matrix

F_(e): mean value of column vectors representing main body structuresupport forces or physical quantities proportional to them

f_(e): variations in column vectors representing main body structuresupport forces or physical quantities proportional to them

dx_(e): another error

C: offset value.

Constant terms are subtracted from the two sides of equation (6) toobtain

dx−dx ₀ =Af _(e) +dx _(e)  (7)

At this time, the coefficient matrix estimate A is obtained to minimizethe sum of squares of the correction residual dx_(e).

More specifically, the estimate A can be obtained using a pseudo inversematrix:

A=(dx−dx ₀)pinv(f _(e))  (8)

where pinv(*) is the pseudo inverse matrix.

The relative error between a stage position measurement value and focusmeasurement device caused by elastic deformation of the main bodystructure can be removed by a correction vector calculated from theproduct of the obtained coefficient matrix A and the column vectorrepresenting a main body structure support force which is alwaysmeasured or a physical quantity proportional to it.

Note that correction cannot be accurately done if measurement of themain body structure support force or physical quantity proportional toit, and measurement of the z-tilt sensor or focus measurement have atiming difference. For this reason, these measurements aresimultaneously done.

The present invention can remove, by correction, variations in stageposition measurement errors, variations in alignment measurement errors,and variations in focus measurement errors, which are caused by changesin force for supporting the main body structure or controllingvibrations and changes in the stage drive force. Hence,high-reproducibility measurement can be realized without increasing therigidity of the main body structure.

As a matter of course, the offset values of stage position measurementerrors, alignment measurement errors, and focus measurement errorscannot be removed by only an application of the present invention.However, these offset values can be removed by adjustment based onperformance evaluation tests.

Embodiments of the present invention will be described below withreference to the accompanying drawings.

<Fifth Embodiment>

In the fifth embodiment shown in FIGS. 11, 12, and 13, the presentinvention is applied to correction of focus measurement errors in theprojection exposure apparatus.

FIG. 11 shows the whole arrangement of a projection exposure apparatusaccording to the fifth embodiment. In FIG. 11, reference numeral 1001denotes a projection lens; 1002, a main body structure; 1003, a waferstage laser interferometer; 1004, a focus measurement device; 1007, awafer; 1008, an x-axis laser interferometer mirror; 1010, a wafer stagetop plate; 1015, an x-y stage; 1033, a load cell; and 1034, a supportbase.

FIG. 12 shows the arrangement of the wafer stage in FIG. 11. In FIG. 12,reference numeral 1007 denotes a wafer; 1008, an x-axis laserinterferometer mirror; 1009, a y-axis laser interferometer mirror; 1010,a wafer stage top plate; 1015, an x-y stage; 1018, an x-axis slider;1019, a y-axis slider; 1020, a y-axis drive linear motor movableelement; 1021, a y-axis drive linear motor stator; and 1022, a waferstage surface plate.

FIG. 13 is a sectional view taken along a line A—A′ in FIG. 12. In FIG.13, reference numeral 1011 denotes a z-tilt actuator; 1012, a θ-z stage;1013, a θ-z guide; 1014, a θ-z actuator; 1016, an x-axis drive linearmotor movable element; and 1017, an x-axis drive linear motor stator.

In this arrangement, the stage is moved to a position where focusmeasurement can be done, and then the z-tilt position and posture areadjusted. In this state, the stage is aligned.

Note that no value of the focus measurement device is fed back. Instead,the relative distance and relative posture between the wafer stage topplate 1010 and θ-z stage 1012 are feedback-controlled by a distancemeasurement device (not shown) to keep the aligned state constant.

If the main body structure does not deform at all, the focus measurementdevice continuously outputs a constant measurement value.

If the main body structure support force is varied to typicallyelastically deform the main body structure and change the measurementvalue of the focus measurement device, variations in focus measurementvalue, i.e., variations in measurement error become equal to the linearsum of variations in the main body structure support force.

In other words, if support forces measured at all points for supportingthe main body structure are multiplied by any coefficient matrix, focusmeasurement errors can be predicted.

A method of obtaining this coefficient matrix will be described.

While the stage is aligned, the support forces of respective supportlegs are varied one by one. The vibration wave preferably includes manylow-frequency components. For example, the vibration wave may includethe cumulation of pink or random noise components.

As a detailed example, a vibration method using a pneumatic spring typevibration reduction leg that is often used in the support base of theprojection exposure apparatus will be described.

In FIG. 14, the vibration reduction leg comprises a housing 1039attached to a support column 1035 via a horizontal pneumatic spring1036, a horizontal balance spring 1038, and a vertical pneumatic spring1037, which face each other. Air amounts supplied to the pneumaticsprings 1036 and 1037 via an air supply path 1047 are controlled bycontrolling control valves 1040 by control signals 1044 output fromcontrol valve controllers 1041 which receive the measurement values ofthe level of the housing 1039 and the pressures of the pneumatic springs1036 and 1037 as feedback signals 1045. To vary the support forces ofthe respective pneumatic springs in the pneumatic spring type vibrationreduction base, a vibration signal 1043 output from a wave generator1042 is switched by a switch 1046 or the like and added to therespective control signals 1044.

The support forces of the respective support legs may be simultaneouslyvaried. In this case, waveforms added to the respective control signalsmust be independent of each other.

As data to be measured, all support forces and the value of the focusmeasurement device are simultaneously measured regardless of thevibration method.

The support force in each direction is preferably measured using theload cell 1033, but can be measured using a pressure gauge for measuringthe pressure of each pneumatic spring because a measurement valueproportional to variations in the support force can be attained.

The measurement values are substituted into equation (3) to obtain thecoefficient matrix A. Using this coefficient matrix, the measurementerror of the focus measurement device caused by variations in the mainbody structure support force can be predicted and corrected.

Since the coefficient matrix changes depending on the wafer shotposition, a coefficient matrix calculated at a representative shotposition is desirably interpolated and approximated in accordance with ashot position. If the coefficient matrix is considered to be constantregardless of the stage position, it need not be interpolated andapproximated. A support force which hardly influences measurement errorsmay be removed from measurement targets. Instead of measuring thesupport force, a physical quantity proportional to variations in thesupport force may be measured.

In an application of the present invention, a predicted measurementerror is removed from the focus measurement value in real time.

<Sixth Embodiment>

In the sixth embodiment shown in FIG. 15, the present invention isapplied to correction of TTL off-axis scope measurement errors in theprojection exposure apparatus.

In FIG. 15, reference numeral 1001 denotes a projection lens; 1002, amain body structure; 1003, a wafer stage laser interferometer; 1005, aTTLoff-axis scope; 1007, a wafer; 1008, an x-axis laser interferometermirror; 1010, a wafer stage top plate; 1015, anx-y stage; 1023, a TTLoff-axis scopemark; 1033, a load cell; and 1034, a support base.

In this arrangement, the stage is moved to a position where the TTLoff-axis scope 1005 can measure the TTL off-axis scope mark 1023 at eachshot, and then the z-tilt position and posture are adjusted. In thisstate, the support forces of respective support legs are varied one byone. The vibration method is the same as in the fifth embodiment.

As data to be measured, all support forces and the value of the TTLoff-axis scope 1005 are simultaneously measured regardless of thevibration method.

The measurement values are substituted into equation (3) to obtain thecoefficient matrix A. Using this coefficient matrix, the measurementerror of the TTL off-axis scope caused by variations in the main bodystructure support force can be predicted and corrected.

Since the coefficient matrix changes depending on the wafer shotposition, a coefficient matrix calculated at a representative shotposition is desirably interpolated and approximated in accordance with ashot position. If the coefficient matrix is considered to be constantregardless of the stage position, it need not be interpolated andapproximated. A support force which hardly influences measurement errorsmay be removed from measurement targets. Instead of measuring thesupport force, a physical quantity proportional to variations in thesupport force may be measured.

In an application of the present invention, a predicted focusmeasurement error is removed from the TTL off-axis scope measurementvalue in real time.

<Seventh Embodiment>

In the seventh embodiment shown in FIG. 16, the present invention isapplied to correction of off-axis scope measurement errors in theprojection exposure apparatus.

In FIG. 16, reference numeral 1001 denotes a projection lens; 1002, amain body structure; 1003, a wafer stage laser interferometer; 1006, anoff-axis scope; 1007, a wafer; 1008, an x-axis laser interferometermirror; 1010, a wafer stage top plate; 1015, an x-y stage; 1024, anoff-axis scope mark; 1033, a load cell; and 1034, a support base.

In this arrangement, the stage is moved to a position where the off-axisscope 1006 can measure the off-axis scope mark 1024 at each shot, andthen the z-tilt position and posture are adjusted. In this state, thesupport forces of respective support legs are varied one by one. Thevibration method is the same as in the fifth embodiment.

As data to be measured, all support forces and the value of the off-axisscope 1006 are simultaneously measured regardless of the vibrationmethod.

The measurement values are substituted into equation (3) to obtain thecoefficient matrix A. Using this coefficient matrix, the measurementerror of the off-axis scope caused by variations in the main bodystructure support force can be predicted and corrected.

Since the coefficient matrix changes depending on the wafer shotposition, a coefficient matrix calculated at a representative shotposition is desirably interpolated and approximated in accordance with ashot position. If the coefficient matrix is considered to be constantregardless of the stage position, it need not be interpolated andapproximated. A support force which hardly influences measurement errorsmay be removed from measurement targets. Instead of measuring thesupport force, a physical quantity proportional to variations in thesupport force may be measured.

In an application of the present invention, a predicted focusmeasurement error is removed from the off-axis scope measurement valuein real time.

<Eighth Embodiment>

In the eighth embodiment shown in FIG. 17, the present invention isapplied to correction of reticle alignment measurement errors in theprojection exposure apparatus.

In FIG. 17, reference numeral 1001 denotes a projection lens; 1002, amain body structure; 1025, a reticle stage laser interferometer; 1028, areticle alignment scope; 1027, a reticle alignment scope mark; 1029, areticle; 1026, a laser interferometer mirror; 1032, a reticle stage topplate; 1033, a load cell; and 1034, a support base.

In this arrangement, the stage is moved to a position where the reticlealignment scope 1028 can measure the alignment mark 1027 on the reticle1029, and then the z-tilt position and posture are adjusted. In thisstate, the support forces of respective support legs are varied one byone. The vibration method is the same as in the fifth embodiment.

As data to be measured, all support forces and the value of the reticlealignment scope 1028 are simultaneously measured regardless of thevibration method.

The measurement values are substituted into equation (3) to obtain thecoefficient matrix A. Using this coefficient matrix, the measurementerror of the reticle alignment scope 1028 caused by variations in themain body structure support force can be predicted and corrected.

Note that a support force which hardly influences measurement errors maybe removed from measurement targets. Instead of measuring the supportforce, a physical quantity proportional to variations in the supportforce may be measured.

In an application of the present invention, a predicted reticlealignment measurement error is removed from the reticle alignmentmeasurement value in real time.

<Ninth Embodiment>

In the ninth embodiment shown in FIG. 18, the present invention isapplied to correction of TTL on-axis alignment measurement errors in theprojection exposure apparatus.

In FIG. 18, reference numeral 1001 denotes a projection lens; 1002, amain body structure; 1003, a wafer stage interferometer; 1007, a wafer;1025, a reticle stage laser interferometer; 1048, a TTL on-axisalignment scope; 1049, a TTL on-axis alignment scope mark; 1029, areticle; 1026, a laser interferometer mirror; 1032, a reticle stage topplate; 1033, a load cell; and 1034, a support base.

In this arrangement, the stage is moved to a position where a TTLon-axis alignment scope mark on the reticle 1029 and the TTL on-axisalignment scope mark 1049 on the wafer 1007 can be compared and measuredvia the projection lens 1001. In this state, the support forces ofrespective support legs are varied one by one. The vibration method isthe same as in the fifth embodiment.

As data to be measured, all support forces and the measurement value ofthe TTL on-axis alignment scope 1048 are simultaneously measuredregardless of the vibration method.

The measurement values are substituted into equation (3) to obtain thecoefficient matrix A. Using this coefficient matrix, the measurementerror of the TTL on-axis alignment scope 1048 caused by variations inthe main body structure support force can be predicted and corrected.

Note that a support force which hardly influences measurement errors maybe removed from measurement targets. Instead of measuring the supportforce, a physical quantity proportional to variations in the supportforce may be measured.

The TTL on-axis alignment scope 1048 is considered to be on the opticalaxis of exposure and thus not to have any measurement error caused by areference shift. Hence, variations in measurement value of the TTLon-axis alignment scope 1048 can be considered to be caused by therelative error between the measurement errors of the wafer stageinterferometer 1003 and reticle stage interferometer 1025 used formeasurement of the stage position.

In an application of the present invention, a predicted measurementerror is removed from the measurement value of the wafer stageinterferometer or reticle stage interferometer in real time.

As described above, according to the fifth to ninth embodiments, sinceall operating forces which elastically deform the main body structureand resultant measurement errors are predicted and corrected,measurement errors due to the elastic deformation can be corrected as ifa structure having infinitely high rigidity is realized. Therefore, theinfluences of the drive repulsion force of the moving stage mounted onthe main body structure, movement of the barycenter, and vibrations fromthe floor can be avoided.

Recent vibration reduction devices employ an active vibration reductiondevice or vibration reduction device with a linear motor, or suppressdeformation of the main body structure by regulating the vibrationspectrum of the floor itself. However, the present invention does notrequire such a device or regulation, and thus, the vibration reductioncost can be greatly reduced.

<10th Embodiment>

According to present invention, variations in distance between theposition control point and position measurement point are predicted andcorrected using a vector obtained by measuring, by the sensor, aprincipal force acting on the stage or physical quantity proportional toit, and any one of the monitor value of the current value of a motor fordriving the stage and the measurement value of a load cell or straingauge installed at a portion where the drive repulsion force of themotor acts, and multiplying the measurement values of the sensor by anappropriate coefficient matrix.

In this case, an appropriate coefficient matrix must be accuratelyestimated. To meet this demand, a method of estimating the coefficientmatrix will be described in detail.

In the present invention, a command signal is supplied to give the stagedrive force the waveform of white noise or sine wave sweep. Variationsin stage drive force or physical quantities proportional to them aremeasured, while the position is simultaneously measured in a stageposition measurement and another evaluation position measurement.

Since a semiconductor exposure apparatus comprises an alignmentmeasurement device for measuring the wafer position using the opticalaxis of exposure as a reference, the alignment measurement device can beconveniently used as an evaluation position measurement device.

The measurement value vector of the evaluation position measurementdevice is given by

Dx+dx=Dx ₀ +dx ₀ +A(F _(e) +f _(e))+dx _(e)  (9)

where

Dx: column vector representing the mean of values of the evaluationposition measurement device

dx: column vector representing variations in values of the evaluationposition measurement device

Dx₀: column vector representing the mean of differences between thevalues of the stage position measurement device and command values,i.e., positional deviations

dx₀: column vector representing variations in positional deviations

A: coefficient matrix

F_(e): mean value of column vectors representing stage drive forces orphysical quantities proportional to them

f_(e): variations in column vectors representing stage drive forces orphysical quantities proportional to them

dx_(e): another error.

Constant terms are subtracted from the two sides of equation (9) toobtain

dx=dx ₀ +Af _(e) +dx _(e)  (10)

At this time, the coefficient matrix estimate A is obtained to minimizethe sum of squares of the correction residual dx_(e).

More specifically, the estimate A can be obtained using a pseudo inversematrix:

A=(dx−dx ₀)*pinv(f _(e))  (11)

where pinv(*) represents the pseudo inverse matrix.

The error of the stage position measurement value caused by elasticdeformation of the stage can be removed by a correction vectorcalculated from the product of the obtained coefficient matrix A and thecolumn vector representing a stage drive force always measured by thesensor or a physical quantity proportional to it.

Note that correction cannot be accurately done if measurement of thestage drive force or physical quantity proportional to it by the sensor,and measurement of the stage position have a timing difference. Thus,these measurements are preferably simultaneously done.

In this way, at least measurement errors caused by the stage drive forceare corrected in the alignment stage in which a target positionmeasurement point and actual position measurement point have a distance,and this distance changes owing to elastic deformation by the stagedrive force.

In some cases, measurement errors cannot be corrected in ahigh-frequency region where the natural frequency of the stage isexcited. However, this does not pose any serious problem in practicaluse because when the natural frequency of a stage movable element issatisfactorily high or even low, high-frequency components ofmeasurement errors caused by deformation of the stage decrease while thestage shifts to a state in which no stage drive force acts, therebyattenuating high-frequency vibrations, i.e., the stage is at rest ormoves at a constant speed.

In the 10th embodiment, since error components can be predicted, thethroughput can increase while maintaining high superposing precision.With the use of this means, performance demanded for the structureshifts from high rigidity to high reproducibility, and an excessiveincrease in weight of the stage structure can be prevented.

The present invention can be easily practiced only by attaching a sensorfor measuring the stage drive force or physical quantity proportional toit and improving measurement control software without requiring largechanges in design.

A detailed embodiment will be described.

In the 10th embodiment shown in FIGS. 19, 20, and 21, the presentinvention is applied to the wafer stage of a projection exposureapparatus, and the correction coefficient is estimated using analignment TTL off-axis scope as an evaluation position measurementdevice.

In FIG. 19, reference numeral 2001 denotes a projection lens; 2002, amain body structure; 2003, a wafer stage laser interferometer; 2004, aTTL off-axis scope; 2005, a wafer stage; and 2006, a TTL off-axis scopemark. In addition, a sensor (not shown) like the described-above one formeasuring a force acting on the stage or physical quantity proportionalto it is arranged. FIGS. 20 and 21 show the wafer stage 2005 in FIG. 19in detail.

In FIG. 20, reference numeral 2007 denotes a wafer; 2008, an x-axislaser interferometer mirror; 2009, a y-axis laser interferometer mirror;2010, a wafer stage top plate; 2018, an x-axis slider; 2019, a y-axisslider; 2020, a y-axis drive linear motor movable element; 2021, ay-axis drive linear motor stator; and 2022, a wafer stage surface plate.

In FIG. 21, reference numeral 2011 denotes a z-tilt actuator; 2012, aθ-z stage; 2013, a leaf spring guide; 2014, a θ-z actuator; 2015, an x-ystage; 2016, an x-axis drive linear motor movable element; and 2017, anx-axis drive linear motor stator.

Estimation of the coefficient matrix A in the 10th embodiment will beexplained.

The stage is moved to a position where the TTL off-axis scope canmeasure the mark 2006 written on the wafer 2007. In this state, theactuators of the respective axes, i.e., the x-axis linear motor, y-axislinear motor, θ-z-axis actuator, and z-tilt actuator are vibrated inunits of axes, while the drive current values of the respective axes,the measurement values of the x- and y-axes by the TTL off-axis scope,the deviation of the x-axis laser interferometer 2003, the deviation ofa y-axis laser interferometer (not shown), and the deviation of aθ-z-axis laser interferometer (not shown) are measured.

The measurement values are substituted into equation (11) to obtain thecoefficient matrix A. Using a correction vector obtained by multiplyingthis coefficient matrix by the measurement values of the sensor, themeasurement errors of the laser interferometers of the respective axesof the wafer stage caused by elastic deformation by the stage driveforce can be corrected.

Since the coefficient matrix changes depending on the wafer shotposition, a coefficient matrix calculated at a representative shotposition is interpolated and approximated in accordance with a shotposition.

<11th Embodiment>

In the 11th embodiment shown in FIG. 22, the present invention isapplied to an off-axis scope 2023 without intervention of any projectionlens, in place of the TTL off-axis scope in the 10th embodiment.

In this case, correction of the laser interferometer is done inmeasuring global alignment using an off-axis scope mark 2024.

<12th Embodiment>

In the 12th embodiment shown in FIG. 23, the present invention isapplied to the reticle stage of a scanning projection exposureapparatus.

In FIG. 23, reference numeral 2025 denotes a reticle stage laserinterferometer; 2026, a laser interferometer mirror; 2027, a reticlealignment scope mark; 2028, a reticle alignment scope; 2029, a reticle;2030, a linear motor stator; 2031, a linear motor movable element; 2032,a reticle stage; and 2033, an illumination system.

Further, a sensor (not shown) like the described-above one for measuringa force acting on the stage or physical quantity proportional to it isarranged.

Estimation of the coefficient matrix A in the 12th embodiment will beexplained.

The stage is moved to a position where the reticle alignment scope 2028can measure the reticle alignment mark 2027 written on the reticle 2029.In this state, the actuator of each axis, i.e., the y-axis linear motoris vibrated, while the drive current value and the deviation of they-axis laser interferometer of the reticle alignment scope are measured.

The measurement values are substituted into equation (11) to obtain theproportionality coefficient matrix A. Using a correction vector obtainedby multiplying this coefficient matrix by the measurement value of thesensor, the measurement error of the y-axis laser interferometer of thereticle stage caused by elastic deformation by the stage drive force canbe corrected.

As described above, according to the 10th to 12th embodiments, stageposition measurement errors caused by elastic deformation by the stagedrive force can be accurately removed without adding any distancesensor, unlike the prior art. As a result, the stage precision caneasily increase.

Even if the stage drive force increases owing to high stage speeds, therigidity of the stage structure need not be increased, and the stage canattain both high precision and high speeds at high level.

An example of the method of manufacturing a device using theabove-mentioned exposure apparatus and exposure method will be explainedbelow.

FIG. 25 shows the flow in the manufacture of a microdevice(semiconductor chips such as ICs, LSIs, liquid crystal devices, CCDs,thin film magnetic heads, micromachines, and the like). In step 31(circuit design), the circuit design of a semiconductor device is made.In step 32 (manufacture mask), a mask formed with a designed circuitpattern is manufactured. In step 33 (fabricate wafer), a wafer isfabricated using materials such as silicon, glass, and the like. Step 34(wafer process) is called a pre-process, and an actual circuit is formedby lithography using the prepared mask and wafer. The next step 35(assembly) is called a post-process, in which semiconductor chips areassembled using the wafer obtained in step 34, and includes an assemblyprocess (dicing, bonding), a packaging (encapsulating chips), and thelike. In step 36 (inspection), inspections such as operationconfirmation tests, durability tests, and the like of semiconductordevices assembled in step 35 are run. Semiconductor devices arecompleted via these processes, and are delivered (step 37).

FIG. 26 shows the detailed flow of the wafer process. In step 41(oxidation), the surface of the wafer is oxidized. In step 42 (CVD), aninsulating film is formed on the wafer surface. In step 43 (electrodeformation), electrodes are formed by deposition on the wafer. In step 44(ion implantation), ions are implanted into the wafer. In step 45(resist process), a photosensitive agent is applied on the wafer. Instep 46 (exposure), the circuit pattern on the mask is printed on thewafer by exposure using the electron beam exposure apparatus having thealignment system described above. In step 47 (development), the exposedwafer is developed. In step 48 (etching), a portion other than thedeveloped resist image is removed by etching. In step 49 (removeresist), the resist film which has become unnecessary after the etchingis removed. By repetitively executing these steps, multiple circuitpatterns are formed on the wafer. In this embodiment, in the repetitiveprocesses, accurate alignment can be attained without being influencedby processes by optimally setting the acceleration voltage of analignment electron beam, as described above.

According to the manufacturing method of this embodiment, a highlyintegrated semiconductor device, which is not easy to manufacture by theconventional method, can be manufactured at low cost.

As many apparently widely different embodiments of the present inventioncan be made without departing from the spirit and scope thereof, it isto be understood that the invention is not limited to the specificembodiments thereof except as defined in the appended claims.

What is claimed is:
 1. An exposure apparatus, which comprises aprojection optical system for forming an image of a pattern formed on amaster plate, a substrate stage for holding and moving a substrate to beexposed to an imaging position, position measurement means for measuringa position of the master plate or substrate or relative positions of themaster plate and substrate, alignment means for moving the master plateor substrate on the basis of a measurement value of said positionmeasurement means to adjust the position or relative positions, a mainbody structure for holding said projection optical system, saidsubstrate stage, and said position measurement means, and a support basefor supporting said main body structure, said apparatus comprising:measurement means for measuring (i) a variation amount of a principalforce acting between said main body structure and said support base or(ii) a distortion resulting from a force acting on the main bodystructure by a vibration reduction device; and correction means forcorrecting a measurement value of said measurement means using acorrection vector obtained by multiplying the measurement result of saidmeasurement means by a predetermined coefficient matrix.
 2. Theapparatus according to claim 1, wherein said measurement means includesat least one of a stage position measurement device for measuring aposition of said substrate stage, a focus measurement device formeasuring a shift in position or posture of a substrate surface withreference to the imaging position, and an alignment scope for measuringan alignment mark on the substrate so as to superpose a new pattern on apattern which has been printed on the substrate surface.
 3. Theapparatus according to claim 2, wherein said alignment scope is one of aTTL on-axis alignment scope for measuring relative positions ofalignment marks on the master plate and substrate using light passing onan optical axis of said projection optical system, a TTL off-axisalignment scope for measuring the relative positions of the alignmentmarks on the master plate and substrate using light passing off theoptical axis of said projection optical system, and an off-axisalignment scope for measuring the position of the alignment mark on thesubstrate outside said projection optical system.
 4. The apparatusaccording to claim 2, wherein said alignment scope is a reticlealignment scope for measuring a position of a reticle using a mark on areticle as a master plate, and further comprises a reticle stage forholding and moving the reticle to align the reticle.
 5. The apparatusaccording to claim 1, wherein the coefficient matrix is obtained bymeasuring by said measurement means the position of the substrate onsaid substrate stage aligned and controlled to keep a position andposture constant, at the same time applying a forced operating force torespective portions for supporting said main body structure, andregressively analyzing a variation amount of a measurement value of saidmeasurement means with respect to variations in the forced operatingforce.
 6. A stage apparatus comprising: a stage for holding and movingan object; stage position measurement means for measuring a position ofsaid stage; a sensor for measuring a variation amount of a principalforce acting on said stage or an elastic deformation caused by the stagedrive force; and means for correcting a measurement value of the stageposition using a correction vector obtained by multiplying a measurementresult of said sensor by a predetermined coefficient matrix.
 7. Theapparatus according to claim 6, wherein said stage position measurementmeans comprises a laser interferometer and a reflecting mirror.
 8. Theapparatus according to claim 6, wherein said apparatus further comprisesposition measurement means arranged in addition to said stage positionmeasurement means, and the predetermined coefficient matrix is obtainedby regressively analyzing a variation amount of a stage drive force ofeach direction when said stage is moved or a physical quantity acting onthe stage, and a difference between measurement values of said positionmeasurement means and said stage position measurement means.
 9. Theapparatus according to claim 6, wherein said sensor is one of means formonitoring a current value of a motor for driving said stages, a loadcell or a strain gauge, wherein each of the load cell and strain gaugeis arranged at a portion where a drive repulsion force of the motoracts.
 10. An exposure apparatus comprising said stage apparatus definedin claim 6, and means for exposing a wafer or reticle mounted on saidstage apparatus.
 11. A semiconductor device manufacturing methodcomprising: a step of manufacturing a device using an exposureapparatus, which comprises a projection optical system for forming animage of a pattern formed on a master plate, a substrate stage forholding and moving a substrate to be exposed to an imaging position,position measurement means for measuring a position of the master plateor substrate or relative positions of the master plate and substrate,alignment means for moving the master plate or substrate on the basis ofa measurement value of the position measurement means to adjust theposition or relative positions, a main body structure for holding theprojection optical system, the substrate stage, and the positionmeasurement means, and a support base for supporting the main bodystructure; a measurement step of measuring (i) a variation amount of aprincipal force acting between the main body structure and the supportbase or (ii) a distortion resulting from a force acting on the main bodystructure by a vibration reduction device; and a correction step ofcorrecting a measurement value of said measurement step using acorrection vector obtained by multiplying the measurement result of saidmeasurement step by a predetermined coefficient matrix.
 12. A devicemanufacturing method comprising: an application step of applying aphotosensitive agent to a substrate; an exposure step of exposing thesubstrate; a step of developing the substrate that has been exposed insaid exposure step; and a step of manufacturing a device using a stageapparatus including a stage for holding and moving an object, stageposition measurement means for measuring a position of the stage, asensor for measuring a variation amount of a principal force acting onthe stage or an elastic deformation caused by the stage drive force, andmeans for correcting a measurement value of the stage position using acorrection vector obtained by multiplying a measurement result of thesensor by a predetermined coefficient matrix, wherein the stage positionmeasurement means comprises a laser interferometer and a reflectingmirror.